It is well known that when an engine of an automobile is not able to be started due to insufficient electric power, a battery of the automobile can be charged by power from a battery of another automobile to thereby start the engine.
To charge the battery of the automobile which is of insufficient electric power by power from a battery of another automobile one must connect the two batteries through a pair of electric wires. This, however, is very dangerous to one who is not familiar with electricity. A battery has a small internal resistance, and there is a voltage difference between a battery with sufficient electric power and a battery without sufficient electric power. Hence, even if the two batteries are connected correctly (which means that electrodes of corresponding polarities are connected respectively), a large current will pass through the electric wires. If the two batteries are connected erroneously (which means that electrodes of the two batteries are not correspondingly connected, or one or both of the batteries are short-circuited), a current which passes through the electric wires will be 10 to 20 times larger than the current existing on the electric wires when the batteries are correctly connected. Under such circumstances the battery(ies) may be damaged, and most important of all, a person who handles the connection between the batteries may get hurt.
It is thus desired to have a device which can be used to connect the two batteries safely;
The device is referred to here as a "safety charging connector".